Transmission jerk?

I have had this car now for over 2 years and every since I have had the car there has been this problem of a jerk in the transmission. This problem is an intermittent one that does not occur every single time. The problem comes and goes. There has been no check engine light and when I run a diagnostic scan with my code scanner I get no codes. The only codes that have ever showed up has been a 0720 I believe. Whenever I have taken the car to a shop they have never been able to pinpoint the problem. There has been talk of replacing the output sensor in the transaxle and that would run some expense. This jerking usually occurs at lower speeds and like I said it comes and goes. I dont know of anything else I can do. The car has been tuned up and runs fine except for the problem that occurs in the transmission. Any ideas as to what it could be? Should I replace the sensor?